This invention relates to an apparatus and method for phase separated synthesis, and in particular to an apparatus and method for continuous phase separated synthesis of particulates. Particularly this invention relates to an apparatus and method for continuous polymerisation.
This invention further relates to an improved apparatus and method for phase separated synthesis of particulates in a batch process and in particular to a crystallisation method and apparatus.
In this field it is known to perform phase separated synthesis of any kind in a batch process. Processes such as polymerisation or crystallisation are normally carried out in a stirred tank reactor (STR). A STR is exclusively operated in a batch mode. Phase separated synthesis generally requires mixing of fluid which, in an STR, is carried out by a mechanically agitated impeller or impellers.
In an STR, mixing of fluid in the vicinity of an impeller is more intensive and of higher shear rates than mixing of fluid distant from the impeller, e.g. adjacent the walls of the tank. This gradient of mixing intensity in the STR results in poor performance in processes relating to particulates, and results in particles of a wider size distribution than is desirable.
A batch process is a complete distinct process. It is necessary to have downtime between batches during which the apparatus in which the process takes place is cleaned. This is inefficient in large scale processes such as polymerization.
It is known to produce liquid polymers by continuous polymerization. Such a process, using a pulsatile flow reactor is described in EPO 0540180. However, that process is restricted to the single phase synthesis of a specific polymer. In addition, the process must be completed in a single pass of the reactor vessel before the vessel becomes fouled, or the process must be regularly halted to purge the reactor vessel.
It is an object of the present invention to provide a apparatus and method for phase separated synthesis of particulates in a continuous manner.
It is a further object of the present invention to provide an improved apparatus and method for phase separated synthesis of particulates in a batch operation.
According to the present invention there is provided an apparatus for polymerization comprising:
a reactor vessel;
supply means to supply a substantially continuous feed of an aqueous medium through the reactor vessel; and
oscillation means to oscillate liquid within the reactor vessel, said reactor vessel comprising:
an inlet in communication with said supply means;
an outlet adaptable for communication with said supply means;
a plurality of stationary baffles; and
at least one port for the introduction of process components and or initiators; characterized in that said reactor vessel comprises purging means to deter fouling, thereby adapting said apparatus for phase separated synthesis of particulates in a continuous manner.
Typically said reactor vessel comprises a plurality of ports for the introduction of process components and/or initiators. Preferably said ports are spaced apart from said oscillation means.
Preferably said outlet is adaptable for communication with a drain.
Preferably said reactor vessel comprises a plurality of substantially parallel tubular sections connected in series.
Preferably said oscillation means comprises a chamber and a diaphragm. More preferably said oscillation means comprises bellows.
Preferably said baffles are annular.
Preferably said baffles have a free area ratio of approximately 10-30%, especially approximately 20%, for example 21%.
Typically the baffles are equally spaced with a spacing of 1-2D where D is the diameter of the reactor vessel, for example, 1.8D.
The apparatus may further comprise temperature control means to vary the temperature of the reactor vessel. Preferably said temperature control means comprises a water-filled jacket. Said jacket may substantially surround said reactor vessel. Said jacket may extend substantially the length of said reactor vessel.
Preferably said vessel is of stainless steel.
Preferably said baffles are of stainless steel.
Preferably said apparatus further comprises premixing means to mix a process component and an initiator or initiators prior to their introduction to the reactor vessel. Said premixing means may comprise a stirred tank reactor. Alternatively said premixing means may comprise a reactor vessel comprising a plurality of baffles; and drive means to oscillate said baffles to mix the process component and the initiator or initiators. More preferably said apparatus comprises a plurality of premixing means.
Preferably said supply means comprises a reservoir positioned above the level of the reactor vessel.
Further according to the present invention there is provided a method of polymerization comprising the steps of:
feeding an aqueous medium substantially continuously through a reactor vessel comprising a plurality of stationary baffles;
supplying a fluid containing at least one process component and an initiator or initiators to the vessels; and
oscillating the liquid within the reactor vessel; characterised in that said method comprises the step of introducing an inert gas to the medium to purge the medium to facilitate the phase separated synthesis of particulates of specified size in a continuous manner.
Further according to the present invention there is provided a method of polymerization in a continuous manner comprising the steps of:
feeding an aqueous medium substantially continuously through a reactor vessel comprising a plurality of stationary baffles;
supplying a fluid containing at least one process component and an initiator or initiators to the reactor vessel; and
oscillating the fluid in the reactor vessel to produce particulates of specified size.
Preferably said method employs an oscillation rate of the medium of between 1 and 4 Hz. Typically the method employs an oscillation amplitude in the reactor vessel of between 0 and 20 mm.
Preferably said method includes the step of premixing a process component with an initiator prior to their supply to the reactor vessel. Said method may include the step of premixing a monomer with an initiator prior to their supply to the reactor vessel. Said method may include the step of premixing a surfactant or surfactants with an initiator prior to their supply to the reactor vessel. Said method may include the step of premixing a colloid with an initiator prior to their supply to the reactor vessel.
The method may include the step of altering the temperature of the reactor vessel.
Preferably the method is employed to produce polyacrylamide or polymethylmethacrylate or polystyrene or similar.
Further according to the present invention there is provided an apparatus for phase separated synthesis of particulates in a batch process comprising:
a reactor vessel comprising a plurality of baffles; and
drive means to oscillate said baffles to mix fluid in the reactor vessel.
Typically said reactor vessel is tubular.
Preferably said baffles are annular.
Preferably said baffles have a free area of approximately 10-40%, especially approximately 20%, for example 21%.
Typically the baffles are equally spaced with a spacing of 1.25-2D, where D is the diameter of the reactor vessel, for example 1.5D.
The apparatus may further comprise temperature control means to vary the temperature the contents of the reactor vessel. Preferably said temperature control means comprises a water-filled jacket. Preferably said jacket surrounds the reactor vessel.
Typically said apparatus is adaptable for phase separated synthesis in a large scale, for example with a reactor vessel of 0.1 to 5 m in diameter.
Preferably said apparatus may be adapted merely to mix solutions.
Further according to the present invention there is provided a method of phase separated synthesis of particulates in a batch process comprising the steps of introducing fluid-based process components in a reactor vessel comprising a plurality of annular baffles adapted for reciprocal motion; and reciprocating said baffles.
Further according to the present invention there is provided a method of mixing solutions comprising the steps of introducing the solutions to a reactor vessel comprising a plurality of annular baffles adapted for reciprocal motion; and reciprocating said baffles.
Embodiments of the present invention will now be described by way of example only with reference to the following examples and the accompanying drawings in which: